$width: 150px;
$height: 150px;
$length: 150px;
.td-cube {
    width: 500px;
    height: 500px;
    perspective: 1000px;
    transform-style: preserve-3d;
}
ul{
    position: relative;
    width: 100%;
    height: 100%;
    transform: rotateX(-15deg) rotateY(15deg);
    transform-style: preserve-3d;
    animation: rotate 5s infinite linear;
}
li{
    display: flex;
    position: absolute;
    justify-content: center;
    align-items: center;
    width: 150px;
    height: 150px;
    opacity: .8;
    font-size: 50px;
    color: #fff;
}
.front {
    background-color: #f66;
    transform: translateZ(150px / 2);
}
.back {
    background-color: #66f;
    transform: rotateY(180deg) translateZ(150px / 2);
}
.top {
    background-color: #f90;
    transform: rotateX(90deg) translateZ(150px / 2);
}
.bottom {
    background-color: #09f;
    transform: rotateX(-90deg) translateZ(150px / 2);
}
.left {
    background-color: #9c3;
    transform: rotateY(-90deg) translateZ(150px / 2);
}
.right {
    background-color: #3c9;
    transform: rotateY(90deg) translateZ(150px / 2);
}
@keyframes rotate {
    from {
        transform: rotateY(0) rotateX(0);
    }
    to {
        transform: rotateY(-1turn) rotateX(-1turn);
    }
}